Method for making poly-etherimides and products produced thereby

ABSTRACT

A method is provided for making polyetherimides involving the reaction of aromatic bis(ether anhydride)s and organic diamines in the presence of a phenolic solvent. The resulting polyetherimide-phenolic solvent mixture can be employed as a wire coating enamel.

This is a division, of application Ser. No. 372,769, filed June 22,1973, now U.S. patent No. 3,917,643.

The present invention relates to polyetherimides which can be made byeffecting reaction between an aromatic bis(ether anhydride) and anorganic diamine in a phenolic solvent.

Prior to the present invention, polyimides derived from the reaction oforganic dianhydrides and organic diamines were generally thermoset andmade by producing an intermediate polyamide acid. As shown by EdwardsU.S. Pat. No. 3,179,614, the polyamide acid is preferably obtained byreacting the organic dianhydride and the organic diamine with a dipolaraprotic solvent at temperatures of 50° C or below. One of the reasonsfor careful temperature control is that premature formation of water ofreaction leads to depolymerization of polymer. In addition, imidizationoccurs as soon as the temperature exceeds optimum limits which candecrease polymer solubility and solution shelf life.

As shown by our copending application Ser. No. 538,112, filed Jan. 2,1975, which is a continuation application of 451,966, filed Mar. 18,1974, now abandoned, which is a continuation-in-part application of Ser.No. 319,371, filed Dec. 29, 1972, now abandoned, and assigned to thesame assignee as the present invention, certain polyimides, such aspolyetherimides can be made by effecting reaction between an aromaticbis(ether anhydride) and an organic diamine in the presence of an inertorganic solvent such as ortho-dichlorobenzene at temperatures of atleast 130° C. Although polyetherimides can be made at elevatedtemperatures, often a plural phase mixture of inert organic solvent andpolyetherimide results, particularly when the reaction mixture isallowed to cool to room temperature. In addition, the water of reactionand the immiscible ortho-dichlorobenzene can cause foaming andcomplicate recovery of the polyetherimide. As a result, and addedseparation step is required before the polyetherimide can be used if thehigh temperature method is employed.

The present invention is based on the discovery that reaction betweensubstantially equal molar amounts of aromatic bis(ether anhydride)s ofthe formula, ##STR1## and organic diamine of the formula,

    H.sub.2 NR.sup.1 NH.sub.2                                  II

in the presence of a phenolic solvent produces a solution which remainshomogeneous when the mixture is allowed to cool to room temperature.There is obtained a solution of polyetherimide in the phenolic solventwhich can be used directly as a wire coating enamel or for applyingpolyetherimide onto various substrates. If desired, the polyetherimidecan be recovered by effecting its separation from the phenolic solventmixture with a non-solvent for polyetherimide, such as methanol.

As shown in formula I, R is a member selected from the class consistingof (a) the following divalent organic radicals: ##STR2## and (b)divalent organic radicals of the general formula where X is a memberselected from the class consisting of divalent radicals of the formulasand -S-, where m is 0 or 1, y is a whole number from 1 to 5, and R¹ is adivalent organo radical selected from the class consisting of (a)aromatic hydrocarbon radicals having from 6-20 carbon atoms andhalogenated derivatives thereof, (b) alkylene radicals, C.sub.(2-8)alkylene terminated polydiorganosiloxane cycloalkylene radicals havingfrom 2-20 carbon atoms, and (c) divalent radicals included by theformula, where Q is a member selected from the class consisting of##STR3## and x is a whole number from 1 to 5 inclusive, and m is aspreviously defined.

There is provided by the present invention, a method for making apolyetherimide, which comprises,

1. effecting reaction between aromatic bis(ether anhydride) of formula Iand organic diamine of formula II, in the presence of a phenolic solventat temperatures between about 100° C to 250° C while effecting theremoval of water of reaction,

2. separating said polyetherimide from the resulting mixture of (1).

There is also provided by the present invention, a wire coating enamelhaving a viscosity of from 200 to 2000 centipoises at 25° C, comprisinga solution of polyetherimide in a phenolic solvent, where thepolyetherimide consists essentially of from 2 to 500, and preferablyfrom 10 to 200 of chemically combined units of the formula, ##STR4##where R and R¹ are as previously defined. As used above, andhereinafter, the term "phenolic solvent" includes phenol and mixtures ofo-, p- and m-cresols known as cresylic acid and mixtures of cresylicwith phenol. In addition phenolic solvent also includes ethylphenols,isopropylphenols, ter-butylphenols, xylenols, chlorophenols,dichlorophenols, phenylphenols, etc. The wire coating enamels of thepresent invention can have from 1 to 40 parts of polyetherimide, per 100parts of phenolic solvent.

Included by the aromatic bis(ether anhydride)s of formula I arecompounds having the formulas, ##STR5##

Dianhydrides included by formula IV are, for example,

2,2-bis[4-(2,3-dicarboxyphenoxy)phenyl]propane dianhydride;

4,4'-bis(2,3-dicarboxyphenoxy)diphenyl ether dianhydride;

1,3-bis(2,3-dicarboxyphenoxy)benzene dianhydride;

4,4'-bis(2,3-dicarboxyphenoxy)diphenyl sulfide dianhydride;

1,4-bis(2,3-dicarboxyphenoxy)benzene dianhydride;

4,4'-bis(2,3-dicarboxyphenoxy)diphenylsulfone dianhydride.

Dianhydrides included by formulas V and VI are, for example,

2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride;

4,4'-bis(3,4-dicarboxyphenoxy)diphenyl ether dianhydride;

4,4'-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride;

1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride;

1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride;

4,4'-bis(3,4-dicarboxyphenoxy)diphenylsulfone dianhydride;

4-(2,3-dicarboxyphenoxy)-4'(3,4-dicarboxyphenoxy)diphenyl-2,2-propanedianhydride, etc.

In addition to formulas IV-V above, aromatic bis(ether anhydride)s alsoincluded by formula I are shown by Koton, M. M.; Florinski, F. S.;Bessonov, M. I.; Rudakov, A. P. (Institute of Heteroorganic Compounds,Academy of Sciences, USSR) USSR 257,010, 11 Nov. 1969, Appl. 03 May1967. In addition dianhydrides shown M. M. Koton, F. S. Florinski, ZhOrg. Khin 4(5) 774 (1968).

Some of the aromatic bis(ether anhydride)s of formula I are shown incopending application of Darrell Heath and Joseph Wirth, Ser. No.281,749, filed Aug. 18, 1972, now U.S. Pat. No. 3,972,902, and assignedto the same assignee as the present invention. These diahydrides can beprepared from the hydrolysis, followed by dehydration, of the reactionproduct of a nitro-substituted phenyl dinitrile with a metal salt of adihydric phenol compound in the presence of a dipolar aprotic solvent.For example, a benzenoid compound of the formula, ##STR6## where the NO₂group can be positioned anywhere in the benzene ring, can be reacted indimethylformamide with an alkali metal salt of a dihydric phenol of thegeneral formula,

    Alk-O-R.sup.2 -O-Alk

where R² is a divalent aromatic radical and Alk is an alkali metal ion.Various well known procedures can be used to convert the resultingtetranitriles to the corresponding tetra-acids and dianhydrides.

Included by the alkali metal salts of the above described dihydricphenols are sodium and potassium salts of the following dihydricphenols:

2,2-bis(2-hydroxyphenyl)propane;

2,4'-dihydroxydiphenylmethane;

bis(2-hydroxyphenyl)methane;

2,2-bis(4-hydroxyphenyl)propane hereinafter identified as "bisphenol-A"or "BPA";

1,1-bis(4-hydroxyphenyl)ethane;

1,1-bis(4-hydroxyphenyl)propane;

2,2-bis(4-hydroxyphenyl)pentane;

3,3-bis(4-hydroxyphenyl)pentane;

4,4'-dihydroxybiphenyl;

4,4'-dihydroxy-3,3'-tetramethylbiphenyl;

2,4'-dihydroxybenzophenone;

4,4'-dihydroxydiphenyl sulfone;

2,4'-dihydroxydiphenyl sulfone;

4,4'-dihydroxydiphenyl sulfoxide;

4,4'-dihydroxydiphenyl sulfide;

3,4'-dihydroxyldiphenylmethane;

4,4'dihydroxybenzophenone;

4,4'-dihydroxydiphenyl ether; hydroquinone;

resorcinol, etc.

Included by the organic diamines of formula II,

are, for example,

m-phenylenediamine;

p-phenylenediamine;

4,4'-diaminodiphenylpropane;

4,4-diaminodiphenylmethane; benzidine;

4,4'-diaminodiphenyl sulfide;

4,4'-diaminodiphenyl sulfone;

4,4'-diaminodiphenyl ether;

1,5-diaminonaphthalene;

3,3'-dimethylbenzidine;

3,3'-dimethoxybenzidine;

2,4-bis(β-amino-t-butyl)toluene;

bis(p-β-amino-t-butylphenyl)ether;

4,4'-diaminobenzophenone;

bis(p-β-methyl-o-aminopentyl)benzene;

1,3-diamino-4-isopropylbenzene;

1,2-bis(3-aminopropoxy)ethane;

m-xylylenediamine;

p-xylylenediamine;

2,4-diaminotoluene;

2,6-diaminotoluene;

bis(4-aminocyclohexyl)methane;

3-methylheptamethylenediamine;

4,4-dimethylheptamethylenediamine;

2,11-dodecanediamine;

2,2-dimethylpropylenediamine;

octamethylenediamine;

3-methoxyhexamethylenediamine;

2,5-dimethylhexamethylenediamine;

2,5-dimethylheptamethylenediamine;

3-methylheptamethylenediamine;

5-methylnonamethylenediamine;

1,4-cyclohexanediamine;

1,12-octadecanediamine;

bis(3-aminopropyl)sulfide;

N-methyl-bis(3-aminopropyl)amine;

hexamethylenediamine;

heptamethylenediamine;

nonamethylenediamine;

decamethylenediamine;

bis(3-aminopropyl)tetramethyldisiloxane;

bis(4-aminobutyl)tetramethyldisiloxane; etc.

The polyetherimide reaction products can be reinforced with conventionalsilica fillers, for example, perlite, fume silica, etc., carbonwhiskers, glass fibers, etc. at proportions of from 10 to 60 parts offiller, per 100 parts of polyetherimide.

In the practice of the method of invention, reaction is effected betweenthe aromatic bis(ether anhydride)s and the organic diamines in thepresence of a phenolic solvent.

The order of addition of either reactants is not critical. It ispreferred to effect the reaction of the dianhydride and the organicdiamine in an inert atmosphere such as nitrogen. Experience has shownthat sufficient phenolic solvent should be utilized to provide a solidscontent in the range of about 10% to 50%.

Reaction can be effected at a temperature of from 100° C to 250° C, andpreferably 130° C to 200° C.

In order to provide optimum contact between the aromatic bis(etheranhydride) and the organic diamine, the reaction mixture can be agitatedsuch as by stirring, etc. Substantially equal moles of reactants hasbeen found to provide for optimum molecular weight of polymer; however,there can be employed from 0.5 to 2 moles and preferably 0.9 to 1.1moles of aromatic bis(ether anhydride) per mole of organic diamines foreffective results. It has been found that the polyetherimide can havefrom about 5 to 500 repeating aromatic bis(ether anhydride)-organicdiamine reaction product units and preferably 10 to 200. Terminal aminoand phthalic acid or phthalic anhydride end groups can be present.

Reaction time of the bis(ether anhydride) of formula I and the organicdiamine of formula II can vary from 0.5 to 20 hours depending upon suchfactors as the temperature employed, degree of stirring, nature of thereactants, etc.

During the course of polymer formation, water of reaction iscontinuously removed. The course of the reaction can be readilydetermined by the actual amount of water generated, as a percentage ofthe theoretical. In particular instances, a mixed solvent system can beemployed consisting of a phenolic solvent and a low boiling solventwhich forms an azeotropic mixture with water. The low boiling solventssuch as cyclohexane benzene, toluene, chlorobenzene, etc. can be used.

At the termination of the reaction, recovery of polyetherimide can beeffected by pouring the polymer solution upon cooling into a precipitantsuch as methanol, etc., followed by washing, filtering, etc.

In order that those skilled in the art will be able to practice theinvention, the following examples are given by way of illustration andnot by way of limitation. All parts are by weight.

EXAMPLE 1

A mixture of 2.011 parts of 1,4-bis(2,3-dicarboxyphenoxy)benzenedianhydride and 0.991 part of 4,4'-diaminodiphenylmethane and about 30parts of trichlorobenzene was heated to reflux for one hour. During thetime the mixture was heated, water was continuously removed byazeotropic distillation. Polymer formed during the period of reactionremained insoluble even though the temperature of the mixture was ashigh as 230° C.

The above reaction mixture was then allowed to cool to room temperatureand about 5 parts of meta-cresol and 2 parts of toluene were added. Themixture was reheated to reflux. An additional amount of water wasrapidly formed and the polymer formed during the reaction completelydissolved. The mixture was allowed to cool to room temperature and aviscous polymer solution was obtained. Based on method of preparationthe product was a solution of a polyetherimide. A titer of the solutionwas poured into methanol to effect the precipitation of product. Therewas obtained a light yellow fibrous polyetherimide at a yield of about92.5%. Anal. Calc. for C₃₅ H₂₀ N₂ O₆ ; C, 74.46; H, 3.57; N, 4.96.Found: C, 74.1; H, 3.8; N, 5.3. The polyetherimide consisted essentiallyof repeating units of the formula, ##STR7## The identity of thepolyetherimide was confirmed by its IR-spectrum.

A portion of the above described polyetherimide solution having aviscosity of about 900 centipoises is employed to treat a copper wire. Acopper wire is passed through the polyetherimide solution and then bakedfor 60 minutes at 350° C. There was obtained an insulated copperconductor having valuable characteristics.

EXAMPLE 2

A mixture of 3 parts of 2,2-bis[4-(2,3-dicarboxyphenoxy)phenyl]propanedianhydride and 1.152 parts of 4,4'-diaminodiphenyl ether, about 40parts of phenol and 10 parts of toluene were heated to reflux for 41/2hours. During this period water was continuously azeotroped from themixture. The mixture was then allowed to cool to room temperature. Therewas obtained a solution of polyetherimide consisting essentially ofrepeating units of the formula, ##STR8## having a viscosity of about1100 centipoises at 25° C. The identity of the product was confirmed byits IR spectrum and method of preparation. The polyetherimide was alight yellow fibrous polymer which was made at a yield of about 98.6%after a titer of the solution was precipitated in methanol.

The above polyetherimide solution is employed as a wire coating enamelas described in Example 1 to produce a coated aluminum conductor havingvaluable characteristics.

EXAMPLE 3

A mixture of 3.000 parts of2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, 1.143 partsof 4,4'-diaminodiphenylmethane, about 40 parts phenol and about 10 partstoluene (10 ml) was heated to reflux at 150 to 154° C for 1.25 hoursduring which time the water formed was removed as an azeotrope. Uponcooling, the reaction mixture was poured into methanol to yield fibrousprecipitate of the polymer. The yield was 3.67 part (93.3%). Atransparent, tough film was obtained by casting from chloroformsolution. The IR spectrum of the film showed that the polymer consistsessentially of repeating units of the formula, ##STR9##

EXAMPLE 4

A mixture of 3.000 parts of2,2-bis[4-(2,3-dicarboxyphenoxy)phenyl]propane dianhydride, 1.143 partsof 4,4'-diaminodiphenylmethane, about 10 parts of toluene and about 35parts of technical grade cresylic acid was heated at 170° C for 2 hours,during which time the water formed was removed azeotropically. Thereaction mixture was poured to precipitate fibrous polymer. The yield ofthe polymer was 3.87g (98.3%). The intrinsic viscosity in DMF was 0.47dl/g. Based on method of preparation the polymer consisted of repeatingunits of the formula, ##STR10##

EXAMPLE 5

A mixture of 3.000 parts of2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, 1.143 partof 4,4'-diaminodiphenylmethane, about 10 parts of toluene and about 35parts of technical cresylic acid was heated at 160° C for 2 hours. Thewater formed was removed azeotropically. The polymer was precipitated inmethanol, the yield was 3.78g (96.1%). Based on method of preparationand its infrared spectrum, the polymer consisted essentially ofrepeating units of the formula, ##STR11##

EXAMPLE 6

A mixture of 3.000 parts of2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane, 1.115 parts of4,4'-diaminodiphenyl ether, about 10 parts of toluene and about 50 partsof ortho-chlorophenol was heated to reflux at 150° C for 4 hours. Thewater formed during the reaction was removed by use of a modifiedDean-Stark trap filled with 4 A molecular sieves. A titer of the polymerwas precipitated in methanol, the yield was 3.32 (89.1%). The intrinsicviscosity in DMF was 0.40 dl/g.

A copper conductor is dipped into a portion of the above phenolicsolution of polyetherimide. The wire is then allowed to air dry atambient temperature to produce a valuable insulated conductor.

EXAMPLE 7

A mixture of 6.282 parts of 4,4'-bis(2,3-dicarboxyphenoxy)diphenyl etherdianhydride, 1.374 parts of meta-phenylenediamine, 20 parts ofmeta-cresol and 7 parts of toluene was heated at 140° C for 20 minutesduring which time water formed was removed by azeotropic distillation.The toluene was distilled off and the reaction mixture was heated at160° C for 10 minutes. The resulting viscous solution was cooled anddiluted with about 25 parts of m-cresol. The viscosity of the solutionwas 960 centistokes at 25° C. A titer of the solution was poured intomethanol to precipitate the white fibrous polymer. The intrinsicviscosity of the polymer was 0.25 and glass transition temperature was205° C. Anal. Calc. for C₃₄ H₁₈ N₂ O₇ : C, 72.08; H, 3.20; N, 4.95.Found: C, 71.9; H, 3.5; N, 5.4. Based on the method of preparation andthe above analysis the polymer consists essentially of repeating unitsof the formula, ##STR12##

EXAMPLE 8

A mixture of 1.98 parts of 4,4'-diaminodiphenylmethane, 2.60 parts of2,2-bis[4-(2,3-dicarboxyphenoxy)phenyl]propane dianhydride, 2.60 partsof 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, 40 partsof cresylic acid, and 10 parts of toluene was heated to reflux for 2hours during which time the water formed was continuously removedazeotropically. Toluene was removed by distillation and the reactionmixture was cooled. The resulting viscous, homogeneous polymer solutionhad a viscosity of approximately 1,000 centistokes at 30° C. Thesolution is stable for indefinite time and can be used as a wire coatingenamel. The titer of the solution was poured into methanol and thefibrous polymer precipitated was isolated. The polymer was identified asa polyetherimide derived from 4,4'-diaminodiphenylmethane and the abovetwo bis(ether anhydride)s by IR and nmr spectra.

The above examples are limited to only a few of the very manypolyetherimides which can be made in accordance with the invention, aswell as wire coating compositions made thereby; it should be understoodthat the present invention is broadly directed to polyetherimides madeby effecting reaction between aromatic bis(ether anhydride) of formula Iand organic diamine of formula II in the presence of a phenolic solvent.

What we claim as new and desire to secure by Letters Patent of theUnited States is:
 1. A wire coating enamel having a viscosity of from200 to 2000 centipoises at 25° C comprising a solution of a polyimide ina phenolic solvent where the polyetherimide consists essentially ofchemically combined units of the formula, ##STR13## where R is selectedfrom the class consisting of a. the following divalent organic radicals,##STR14## and b. divalent organic radicals of the general formula,##STR15## where X is a member selected from the class consisting ofdivalent radicals of the formulas -C_(y) H_(2y) -, ##STR16## -O-, and-S-, where m is 0 or 1, y is a whole number from 1 to 5, and R¹ is adivalent organo radical selected from the class consisting of (a)aromatic hydrocarbon radicals having from 6-20 carbon atoms andhalogenated derivatives thereof, (b) alkylene radicals, C.sub.(2-8)alkylene terminated polydiorganosiloxane cycloalkylene radicals havingfrom 2-20 carbon atoms, and (c) divalent radicals included by theformula, ##STR17## where Q is a member selected from the classconsisting of ##STR18## and x is a whole number from 1 to 5 inclusive,and m is as previously defined.
 2. A method for making a wire coatingenamel comprising1. effecting reaction between aromatic bis(etheranhydride) of the formula, ##STR19## and organic diamine of the formula,

    H.sub.2 HR.sup.1 NH.sub.2,

in the presence of a phenolic solvent at temperatures between about 100°C to 250° while effecting the removal of water of reaction, where R isselected from the class consisting of (a) the following divalent organicradicals: ##STR20## and (b) divalent organic radicals of the generalformula ##STR21## where X is a member selected from the class consistingof divalent radicals of the formulas ##STR22## and -S-, where m is 0 or1, y is a whole number from 1 to 5, and R¹ is a divalent organo radicalselected from the class consisting of (a) aromtic hydrocarbon radicalshaving from 6-20 carbon atoms and halogenated derivatives thereof, (b)alkylene radicals, C.sub.(2-8) alkylene terminated polydiorganosiloxanecycloalkylene radicals having from 2- 20 carbon atoms, and (c) divalentradicals included by the formula, ##STR23## where Q is a member selectedfrom the class consisting of ##STR24## and x is a whole number from 1 to5 inclusive, and m is as previously defined.
 3. A method in accordancewith claim 2 where the organic dianhydride is ##STR25##
 4. A method inaccordance with claim 3 where the organic dianhydride is ##STR26## whereR² is as previously defined.